Sun Aijing, Shanmugam Ilanchezian, Song Jiawu, Terranova Paul F, Thrasher J Brantley, Li Benyi
Department of Pathology, Shaoxing People's Hospital and the First Affiliated Hospital of Shaoxing University, Shaoxing, Zhejiang, China.
Prostate. 2007 Jun 15;67(9):976-88. doi: 10.1002/pros.20586.
Lithium is an existing drug for bipolar disorder and its uptake was recently linked to reduced tumor incidence compared to the general population. The major target of lithium action is glycogen synthase kinase 3 (GSK-3). Since GSK-3 expression and activation are associated with prostate cancer progression, the anti-cancer potential of lithium on prostate cancer was investigated in this study.
Multiple prostate cancer cell lines were treated with lithium chloride (LiCl). Cell proliferation and cell cycle distribution were analysed. DNA replication was determined using BrdU labeling assay. Genome-wide screening of gene expression was performed using cDNA microarray assay. GSK-3beta gene-specific silencing was conducted using small interferencing RNA (siRNA) transfection. E2 factor (E2F) transactivation was evaluated using reporter gene assay and E2F-DNA interaction was determined with chromatin-immunoprecipitation assay (ChIP).
LiCl significantly inhibited cell proliferation, which was associated with reduced DNA replication and S-phase cell cycle arrest. LiCl significantly decreased the expression of multiple DNA replication-related genes, including cell division cycle 6 (cdc6), cyclin A, cyclin E, and cdc25C, which are regulated by E2F factor during cell cycle. A novel GSK-3-specific inhibitor TDZD-8 and GSK-3beta siRNA also suppressed the expression of these E2F target genes, indicating that LiCl-induced anti-cancer effect was associated with GSK-3beta inhibition. Furthermore, LiCl suppressed E2F transactivation by interrupting the interaction of E2F1 factor with its target gene promoter.
These data indicated that LiCl suppresses cancer cell proliferation by disrupting E2F-DNA interaction and subsequent E2F-mediated gene expression in prostate cancer.
锂是一种用于治疗双相情感障碍的现有药物，最近研究发现，与普通人群相比，服用锂与肿瘤发病率降低有关。锂发挥作用的主要靶点是糖原合酶激酶3（GSK-3）。由于GSK-3的表达和激活与前列腺癌进展相关，本研究对锂在前列腺癌方面的抗癌潜力进行了调查。
用氯化锂（LiCl）处理多种前列腺癌细胞系。分析细胞增殖和细胞周期分布。使用BrdU标记试验测定DNA复制。使用cDNA微阵列试验进行全基因组基因表达筛选。使用小干扰RNA（siRNA）转染进行GSK-3β基因特异性沉默。使用报告基因试验评估E2因子（E2F）反式激活，并通过染色质免疫沉淀试验（ChIP）确定E2F与DNA的相互作用。
LiCl显著抑制细胞增殖，这与DNA复制减少和S期细胞周期停滞有关。LiCl显著降低了多个与DNA复制相关基因的表达，包括细胞分裂周期6（cdc6）、细胞周期蛋白A、细胞周期蛋白E和cdc25C，这些基因在细胞周期中受E2F因子调控。一种新型的GSK-3特异性抑制剂TDZD-8和GSK-3β siRNA也抑制了这些E2F靶基因的表达，表明LiCl诱导的抗癌作用与GSK-3β抑制有关。此外，LiCl通过中断E2F1因子与其靶基因启动子的相互作用来抑制E2F反式激活。
这些数据表明，LiCl通过破坏前列腺癌中E2F与DNA的相互作用以及随后E2F介导的基因表达来抑制癌细胞增殖。
